It may be that one simply can't use ISO 8601: 2004 this way.  Using 
9999 and 0000 to represent not "dates in the Gregorian calendar" but 
rather a quality of open-endedness with respect to an end date or a 
start date is logically outside of the domain of ISO 8601.  Anything 
we do would be a kluge.

9999 may not be the best value to mean "forever" as it would also 
mean the year 9999. A bit far off to worry about, of course. And OOOO 
would mean 1 BCE (or be illegal) as there is no year 0 between the 
first year of the common era (1 CE) and the last year prior to the 
1st year of the CE (1 BCE).

I think, though, that 0000 is not needed since a way to represent the 
open-endedness of a start date is not needed. The rights related to 
the object can't pre-date the object itself.  So One can simply use a 
practical (albeit) arbitrary start date such as the date of the 
creation of the digital object or, if necessary, the date of the 
original object for which the digital copy is a proxy.

And then--for about 8000 years anyway--9999 may work perfectly well 
being used to mean endless. But, of course, that would be a 
non-standard use of 9999.

Matthew Beacom

p.s. below is the abstract for ISO 8601: 2004 from

ISO 8601:2004 is applicable whenever representation of dates in the 
Gregorian calendar, times in the 24-hour timekeeping system, time 
intervals and recurring time intervals or of the formats of these 
representations are included in information interchange. It includes
    * calendar dates expressed in terms of calendar year, calendar 
month and calendar day of the month;
    * ordinal dates expressed in terms of calendar year and calendar 
day of the year;
    * week dates expressed in terms of calendar year, calendar week 
number and calendar day of the week;
    * local time based upon the 24-hour timekeeping system;
    * Coordinated Universal Time of day;
    * local time and the difference from Coordinated Universal Time;
    * combination of date and time of day;
    * time intervals;
    * recurring time intervals.
ISO 8601:2004 does not cover dates and times where words are used in 
the representation and dates and times where characters are not used 
in the representation.

ISO 8601:2004 does not assign any particular meaning or 
interpretation to any data element that uses representations in 
accordance with ISO 8601:2004. Such meaning will be determined by the 
context of the application.

Matthew Beacom

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